Conical swaging presses typically comprise a housing with an annular axially extending side wall, a front wall with a central opening to enable work to be processed to be introduced into a work zone located rearwardly of the front wall and inwardly of the annular side wall, and a rear wall at least partially closing the space between the front wall, the rear wall, and inwardly of the side wall. Arranged within the work zone are a plurality of die shoes disposed axially circumferentially spaced from one another defining a ring of die shoes. Each die shoe has a radial inner surface adapted to connect to a die element that, in use, engages a work piece (ferrule) during a swaging operation and a radially outer surface engageable with a piston member movable in the axial direction under the influence of hydraulic fluid applied pressure forces. The radially outer surfaces of the die shoes are shaped as a segment of a frustoconical surface or two or more segments of frustoconical surfaces each separated by a joining ramp surface whereby each segment of a frustoconical surface defines a segment of a circular cross-section in transverse cross-section. The piston member presents at least one internally formed frustoconical surface, or two or more such surfaces separated by ramp surfaces, when the die shoes are similarly formed. The inner surfaces of the piston member are designed to engage with the outer faces of the die shoes to force the die shoes radially inwardly as the piston member is forced forwardly during a swaging process. Movement of the piston member in a reverse direction allows the die shoes to move radially outwardly to allow a swaged work piece to be removed from the work zone. In one arrangement compression spring means operable between the die shoes assist with expanding the die set radially outwardly.
Typically, there is necessarily a mismatch between the radius of curvature of the outer faces of the die shoes and the frustoconical surface or surfaces of the piston member at axial positions along the die shoes such that there is axial line contact between the outer surface of the die shoes and the frustoconical surface(s) of the piston member when the press is unloaded, and a narrow axial contact band zone when the press is loaded. Because heavy loads are employed, it is necessary to lubricate the contact regions between the piston member and the die shoes. This is conventionally achieved by applying a suitable lubricating grease to the contact surfaces. With repeated swaging operations the lubricating grease tends to be squeezed towards the axial sides of die shoes progressively decreasing the amount of lubricating grease in the contact zone between the outer surfaces of the die shoes and the frustoconical surfaces of piston member. Generally, with repeated swaging operations, the contact lines or bands between the die shoes and the piston member remain substantially in the same circumferential region of the piston member frustoconical contact surfaces. Eventually, the operation of the swaging press has to be stopped and the press has to be serviced including re-greasing the above discussed contact surfaces. This puts the press out of use for a period of time. If re-greasing of the contact surfaces is not done when required, the press will become more and more inefficient and will eventually seize with potentially catastrophic effects. Attempts to overcome this problem have included using continuous supply liquid lubricants which provide problems and costs in the supply systems used for liquid lubricants and moreover, because of the heavy loads involved, liquid lubricants tend not to work as well as lubricating greases.
While conical type swaging presses are the most common swaging press design in use, it does have radial force limitations as well as the above discussed lubrication difficulties in operation. There has also been some development work in scissor design swaging machines but these machines tend to have a higher cost structure.
In this specification reference will be made to swaging presses and machines but this is intended to also incorporate reference to crimping presses and machines.